When you compare two biometric locks, the marketing will shout about speed and design — but the numbers that truly decide real-world reliability are two you rarely see on the box: FAR and FRR. Together they are the honest measure of fingerprint door lock accuracy, balancing how secure a lock is against how conveniently it lets the right people in.
In this guide, Covlor® explains exactly what False Acceptance Rate and False Rejection Rate mean, what good values look like, how the two are always in tension, and how you can get the best accuracy from your own lock at home.
What Is False Acceptance Rate (FAR)?
False Acceptance Rate is the probability that the lock wrongly accepts someone who is not an enrolled user — in other words, it lets in a stranger. This is purely a security measure: the lower the FAR, the harder the lock is to fool. Quality fingerprint locks aim for an extremely low FAR, often quoted around 0.001% or better, which means the chance of an unauthorised fingerprint being accepted is vanishingly small. When you read a spec sheet, a lower FAR is always better for security.
What Is False Rejection Rate (FRR)?
False Rejection Rate is the opposite problem: the probability that the lock wrongly rejects a genuine, enrolled user. This is a convenience measure — a high FRR means you (or your family) get turned away and have to try again, which is annoying rather than dangerous. A well-designed lock keeps FRR low so you get in first time, every time, even with a slightly wet or cold finger. If a lock constantly makes you re-press the sensor, its FRR is too high.
The Trade-Off Between Them
Here is the key insight: FAR and FRR pull in opposite directions. Make a lock stricter about what counts as a match and you lower the FAR (more secure) but raise the FRR (more rejections). Loosen it and you get the reverse — easier acceptance but weaker security. Every biometric lock therefore chooses an operating point that balances the two. The engineering skill lies in setting that balance so the lock is genuinely secure and pleasant to use, rather than sacrificing one for the other.
How This Applies to Fingerprint and Face
Both fingerprint and face recognition are measured by FAR and FRR, but the factors differ. Fingerprint accuracy depends on sensor quality (capacitive sensors read the ridges of your skin precisely) and how well the print was enrolled. Face recognition accuracy depends on the camera and depth sensing, and on lighting. In both cases, a premium sensor plus good enrolment produces low FAR and low FRR together. You can compare the two methods head to head in our fingerprint vs face guide.
FAR vs FRR at a Glance
| Metric | Measures | Lower Is Better For |
|---|---|---|
| FAR | Wrongly accepting a stranger | Security |
| FRR | Wrongly rejecting a real user | Convenience |
What Good Numbers Look Like
As a rough guide, a strong fingerprint lock targets a FAR around 0.001% or lower and an FRR low enough that rejections are rare in daily use (often quoted around 1% or better). Do not fixate on a single figure, though — a lock advertising an incredibly low FAR but a high FRR will frustrate you daily, while one with a very low FRR but a loose FAR is a security risk. Balance is what matters, and it is why buying from an established brand that tunes both is worthwhile.
Factors That Affect Real-World Accuracy
In everyday life, several things influence how a biometric lock performs. Dirty or worn sensors, dry or damaged fingertips, poor enrolment, and (for face) harsh lighting all push the FRR up. The reassuring part is that most of these are within your control. Keeping the sensor clean and enrolling carefully makes a dramatic difference — more on that below and in our troubleshooting guide.
How to Improve Accuracy at Home
You can meaningfully lower your own false-rejection rate with a few habits. Enrol each finger from several angles and with slightly different pressure so the lock has a complete picture. Register more than one finger per person — an index finger and a thumb — so a small cut or a dry day never locks you out. Wipe the sensor clean every few weeks, since oil and dust are the top cause of misreads. And for face recognition, enrol in even lighting at your normal standing distance.
Why It Matters When You Buy
A lock with strong FAR and FRR figures translates directly into your daily experience: it opens first time for you and your family, and stays firmly shut for everyone else. That combination of dependable convenience and real security is exactly what a smart lock should deliver. Covlor® tunes its CR L51-S and other models for fast, accurate recognition so you enjoy both. Explore the full range.
Frequently Asked Questions
What is a good FAR for a fingerprint lock?
A very low FAR — around 0.001% or better — means the lock rarely accepts an unauthorised fingerprint, keeping it secure.
What causes a high false rejection rate?
Dirty sensors, poorly enrolled prints, dry or damaged fingertips, or harsh lighting for face recognition. Cleaning the sensor and re-enrolling from multiple angles helps.
Are fingerprint locks accurate?
Yes. Quality fingerprint locks combine low FAR and low FRR, making them both secure and reliable for everyday use.
Which is more important, FAR or FRR?
Both matter: FAR protects security while FRR protects convenience. The best locks minimise both together rather than trading one for the other.
Can I improve my lock’s accuracy?
Yes. Enrol multiple fingers from different angles, keep the sensor clean, and re-enrol if reads become inconsistent.
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